Recently, with the development of smart phone-related technology, smart phones have developed to such an extent that the functions and performances thereof compare with those of existing PCs. Thus, it is time to review the relay-based ring-back tone service which was created at the time of 2G phones. The 2G phones had provided the circuit-based voice service instead of the packet-based data service, and the ring-back tone service had been developed at that time. The ring-back tone service is still being used while a large number of mobile-carrier relays directly play contents and provide the contents to mobile terminals through circuit networks.
The packet-based service and the circuit-based service will be briefly described as follows. When communication is intended to be connected between points A and B, the connection passes through a plurality of gateways/routers. Thus, between the points A and B, a plurality of paths may be created depending on combinations. According to the circuit-based service, a path is selected from the plurality of paths when communication is initially connected, and continuously used until the communication is disconnected. In this case, since one path is completely occupied while the path is used, a user bears a communication fee for the path occupation. According to the packet-based service, data are divided into a predetermined size of units (packets), and the packets are transmitted to the destination through different paths and recombined in the original order. The packet-based service has advantages in that data can be transmitted without occupying a predetermined path and a communication fee is determined according to how many packets are transmitted. A representative example of the circuit-based service is the current voice call connection method, and the packet-based service is mainly used for data communication.
The circuit-based service is technically based on the principle that, when music is played from one telephone after two telephones are connected to each other, the music is heard through the other telephone. Such a service is still provided even at this moment that smart phones have been popularized. In the circuit-based service, although high-quality music is played, the sound quality of the music is determined only within a voice call bandwidth. Thus, although recent high-quality MP3 sound sources and high-quality lossless contents are provided, the contents are inevitably serviced according to a narrow bandwidth provided by the circuit network.
Furthermore, when a user sets a ring-back tone under the current service, all persons who make a call to the user must hear the set contents regardless of their intentions. Therefore, all persons inevitably hear the corresponding contents until the call is connected.